CHARLESTON, S.C., Jan. 26 -- Sen. Barack Obama of Illinois won the South Carolina primary in a landslide Saturday, attracting a biracial coalition that gave his candidacy a much-needed boost as the Democratic presidential race moves toward a 22-state showdown on Feb. 5.

Obama trounced Sen. Hillary Rodham Clinton of New York in the first Southern primary of the 2008 campaign, winning 55 percent of the vote to Clinton's 27 percent. Former senator John Edwards of North Carolina was third with 18 percent.

After a bitter and racially charged campaign in which former president Bill Clinton became the center of controversy, Obama won with overwhelming support from African Americans and attracted about a quarter of the white vote, according to exit polling.

"After four great contests, in every corner of this country, we have the most votes, the most delegates and the most diverse coalition of Americans that we've seen in a long, long time," Obama told an enthusiastic crowd of supporters in Columbia who interrupted his victory speech with chants of "Yes, we can!" and "Race doesn't matter!"

Obama depicted the Democratic race as "the past versus the future." But he told supporters they are facing a formidable challenge, and then, alluding to controversies that erupted with the Clintons last week, said, "This is our chance to end it once and for all."

Obama's big victory margin means the battle for the Democratic nomination will continue without a clear front-runner. Obama and Clinton have now split the first four contests of the campaign, and the candidates face the possibility of a conflict that aides in both campaigns said Saturday could stretch into March or even April.

In a move certain to spark more warfare with the Obama campaign, Clinton set her sights on Tuesday's beauty-contest primary in Florida as a way to blunt Obama's South Carolina momentum.

That contest is not sanctioned by the Democratic National Committee, and the candidates earlier agreed not to campaign there. But Clinton, who leads in polls there, signaled Saturday night that she will seek a public relations victory in a state that will turn out more voters than in any contest to date.

Clinton currently leads in a number of the most populous states with contests on Feb. 5, including California and New York, and her campaign has predicted that she will emerge from the competition that day with a lead in convention delegates. Obama hopes to win more states than Clinton on Feb. 5, but he will be equally focused on preventing her from jumping into a big lead in the battle for delegates.

Clinton's campaign had anticipated a loss in South Carolina and sought throughout the week to play down the significance of the vote here. But Obama's victory margin was far larger than her advisers or any pre-primary poll had expected, as Obama demonstrated an ability to energize his supporters on a day when turnout appeared likely to break the previous record for a Democratic primary in the state.

Clinton left South Carolina shortly after the polls closed and delivered her concession speech in Nashville. She briefly offered her congratulations to Obama and then plunged into a version of her standard stump speech. "I want to tell you how excited I am that now the eyes of the country turn to Tennessee and the other states that'll be voting on February 5th and, of course, to the state of Florida that will be voting on Tuesday," Clinton said.

Her husband was campaigning in Missouri, another Feb. 5 state, and said there that Obama had won "fair and square." But before leaving South Carolina, he compared Obama's victory to those of Jesse Jackson in the same state in 1984 and 1988. "Jackson ran a good campaign and Obama ran a good campaign here," he said.

Edwards, who won South Carolina four years ago, appeared to capitalize on the bickering between Clinton and Obama, winning half of the white voters who made up their minds in the final three days.

Edwards hopes to profit from the Clinton-Obama wrangle. But after three consecutive third-place finishes, he now must decide whether continuing his candidacy will result in him becoming a potential power broker or a spoiler.

Speaking to supporters, Edwards vowed to carry his campaign forward to "give voice to millions of Americans who have absolutely no voice in this democracy."

Obama's victory was built on a foundation of support from African Americans. Black voters made up slightly more than half of the Democratic electorate on Saturday, and Obama won about four in five of their votes.

Months earlier, he and Clinton were in a pitched battle for the support of black voters, with Clinton hoping to draw on her and her husband's deep roots in the African American community. But Obama quickly consolidated their support, and his superior organization provided an extra boost that paid off on voting day.

Clinton made a special effort to attract support from African American women, but they were as strong in their support for Obama as were black men. Obama defeated Clinton among black women 4 to 1.

The South Carolina campaign turned into the nastiest stage of the Democratic battle so far. Clinton and Obama traded insults during a rancorous debate in Myrtle Beach on Monday night, and the two campaigns clashed repeatedly over whether the Clintons -- and, in particular, the former president -- were deliberately distorting some of Obama's statements for political advantage.

The attacks raged through much of the week, until Clinton and Obama backed away from the brink on Thursday, but by then the damage was done. The results of the primary were "a sound rejection of the politics of attack and division by the voters of South Carolina," David Plouffe, Obama's campaign manager, said shortly after the polls closed.

Clinton advisers held firm in their argument that it was the Obama campaign that had sought to undermine the former president, and they predicted that the battle in South Carolina will damage Obama going forward.

By 7:37 p.m., barely half an hour after the polls closed, Clinton was in the air headed toward Nashville, her campaign's eagerness to leave South Carolina barely disguised. Although her strategists took care not to disparage the voters of South Carolina -- as they had caucusgoers after losing Iowa weeks earlier -- the private assessment from some supporters was that Obama had won only because of large minority turnout.

Obama's team quickly rebutted that argument, noting that he had solid support in the white community, as well, and the dispute seemed certain to roil the campaign further.

The real battle will be the nearly two dozen states that vote on Feb. 5. Almost 1,700 delegates are at stake that day -- slightly more than half of the pledged delegates to the Denver convention -- and the two campaigns will throw enormous resources into the contest.

"Obama's given himself another chance," said Democratic pollster Mark Mellman, who is unaffiliated. "The question is: How big a bounce does he get out of this? He's going into Super Tuesday behind in a number of major states. . . . He gives himself a chance to get back in the game in a serious way."

The racial makeup of most of those states is far different from South Carolina's, with smaller black populations and larger Latino populations. Clinton carried the Hispanic vote in last Saturday's Nevada caucuses and hopes to repeat that in states such as California, Arizona and New Mexico.

The exit polls in South Carolina showed Obama winning a majority of both men and women, and winning most categories of voters. But there were clear racial splits, with African Americans solidly behind Obama and white voters divided among the three candidates.

Inside the Obama campaign, a nervous energy built in the final days here. Internally, the numbers continued to look solid, but advisers feared that the arguments with the Clintons would tarnish Obama's image as he prepared to pivot to Feb. 5. But as Saturday unfolded, concern gave way to elation. At about 4 p.m., Obama emerged from his downtown Columbia hotel wearing sweats and basketball shoes, headed to a local gym to play with a group of Secret Service agents and staffers.

South Carolina political veterans said Obama's ground organization was one of the best they had seen, consisting of 9,000 volunteers and nearly 150 voting-day staging areas. His operation overlooked no potential source of votes.

Most significantly, Obama virtually swept the African American vote despite rejecting typical tactics deployed in the South; aides said they hadn't paid "street money" to local leaders and community organizers to get people to the polls. Obama campaign officials had bragged about bucking this long-entrenched system, but they weren't certain until Saturday whether it would work.

Kornblut reported from Tennessee with the Clinton campaign. Murray reported from South Carolina with the Obama campaign.